KR102059234B1 - Optical film with pressure-sensitive adhesive and image display device - Google Patents

Abstract

The present invention, when used for bonding to the front transparent plate, provides a pressure-sensitive adhesive sheet having no outgassing and capable of suppressing display unevenness of the image display device, and an optical film provided with a pressure-sensitive adhesive having the pressure-sensitive adhesive sheet. do.
The optical film 53 with an adhesive is provided with the front side adhesive sheet 20 in one surface of the optical film 10. The front side adhesive sheet 20 is a laminated adhesive sheet including the first adhesive layer 21 and the second adhesive layer 22. A first pressure-sensitive adhesive layer 21, the storage elastic modulus at 150 ℃ 9 × 10 ³ ㎩ or lower and a storage elastic modulus G of 20 ℃ 'storage modulus at ₂₀ and ₁₅₀ ℃ G' 150 ratio G _'20 / G of ' ₁₅₀ is more than 20. As for the 2nd adhesive layer 22, the storage elastic modulus in 20 degreeC is 4 * 10 <^5> Pa or less, and the storage elastic modulus in 150 degreeC is 1 * 10 <^4> Pa or more.

Description

Optical film and image display device equipped with an adhesive {OPTICAL FILM WITH PRESSURE-SENSITIVE ADHESIVE AND IMAGE DISPLAY DEVICE}

The present invention relates to an optical film provided with a pressure-sensitive adhesive sheet and a pressure-sensitive adhesive for use in forming an image display device including a transparent plate, a touch panel, and the like on the front surface of an image display panel. Moreover, this invention relates to the image display apparatus using the said adhesive sheet or the optical film with an adhesive.

As various image display devices, such as a mobile telephone, a car navigation device, a monitor for personal computers, and a television, a liquid crystal display device and an organic electroluminescence display are used widely. For the purpose of preventing damage to the image display panel due to an impact from an external surface, a front transparent plate (also called a window layer) such as a transparent resin plate or a glass plate is provided on the visual side of the image display panel. There is a case. Also, in recent years, devices having a touch panel on the viewing side of an image display panel have become popular.

As a method of arranging a front transparent plate, a touch panel and the like on the front surface of an image display panel, an "interlayer filling structure" in which both are bonded through an adhesive layer is employed. In the interlayer filling structure, since the adhesive is filled between the panel and the front transparent member, the difference in refractive index at the interface is reduced, and the decrease in visibility due to reflection and scattering is suppressed. On the peripheral part of the image display panel side surface of the front transparent plate, a colored layer for the purpose of decoration or light shielding is printed, and a printing step of about 10 µm to several tens of µm exists. When a sheet-like adhesive is used as an interlayer filler, an adhesive cannot fully enter in the vicinity of a printing step, a bubble may remain and the visibility of a screen may fall.

In order to solve such a problem resulting from the printing level | step difference, the thickness-thick and soft adhesive sheet is used for the bonding of a front side transparent member, and the printing level | step difference absorption property is performed. For example, in patent document 1, 2, it is described that making the storage elastic modulus of the adhesive layer used for bonding an optical film and a front side transparent plate into a predetermined range. Moreover, in patent document 3, 4, it is described that the adhesive sheet with small residual stress by a tensile stress relaxation test is excellent in level | step difference absorbency.

As described above, when the adhesive sheet having a large thickness and a soft (small storage elastic modulus or residual stress) is used, generation of bubbles in the vicinity of the printing step can be suppressed. On the other hand, when an adhesive is soft, a bubble will remain in the interface of a front transparent member and an adhesive sheet easily. In particular, in recent years, from the viewpoint of weight reduction and flexibility of the members, a front transparent plate made of a resin such as acrylic or polycarbonate is used, and the outgas generated by heating causes the front transparent plate and the adhesive sheet to be used. The problem of staying as an air bubble at the interface with a current is present.

In the said patent document 1, 2, the lamination | stacking adhesive sheet which laminated | stacked two layers of adhesive layers from which storage elastic modulus differs, and joining the adhesive layer which has a relatively high storage elastic modulus with a front transparent plate is a bubble in the printing step vicinity. It is disclosed that the retention of and the bubble retention in the vicinity of the interface due to the outgas from the front transparent plate can be simultaneously solved.

WO2010 / 04229 International Publication Pamphlet Japanese Patent Laid-Open No. 2011-219665 Japanese Patent Laid-Open No. 2011-74308 Japanese Patent Publication No. 2013-6892

When the laminated pressure sensitive adhesive sheet disclosed in Patent Documents 1 and 2 is used for bonding an image display panel with a front plate or a touch panel, air bubbles can be suppressed in the vicinity of a printing step or at an interface, but are displayed at the periphery of the screen. There were cases where problems such as nonuniformity occurred.

In view of the above, the present invention is a pressure-sensitive adhesive sheet capable of suppressing the deterioration of visibility due to the display unevenness and the cloudiness of the pressure-sensitive adhesive, even when used for bonding to a front transparent plate having a printing step, and An object of the present invention is to provide an optical film provided with a pressure-sensitive adhesive having the pressure-sensitive adhesive sheet.

As a result of the present inventors examining, in the adhesive sheet in which the several adhesive layers were laminated | stacked, the storage elastic modulus of each adhesive layer has a predetermined range, and the storage elastic modulus of the adhesive layer formed in the optical film side of an image display apparatus is predetermined | prescribed. In the case of having temperature dependence, it was found that display unevenness was suppressed and the present invention was reached. This invention relates to the lamination | stacking adhesive sheet used for the bonding of an image display panel, a front side transparent plate, and a touch panel, and the optical film with an adhesive provided with the said laminated adhesive sheet on an optical film.

The optical film with an adhesive of this invention is equipped with the front surface side adhesive sheet in one surface of the optical film containing a polarizing plate. A front side adhesive sheet is a laminated adhesive sheet in which at least two adhesive layers were laminated | stacked, and is equipped with the 1st adhesive layer arrange | positioned in contact with an optical film, and the 2nd adhesive layer arrange | positioned most apart from an optical film.

The first pressure-sensitive adhesive layer has a storage elastic modulus at 150 ℃ 9 × 10 ³ and ㎩ or less, a storage elastic modulus G _'20 to the storage elastic modulus G of from ₁₅₀ ℃' 150 ratio G _'20 / G' of from 20 ℃ ₁₅₀ This is over 20. The storage elastic modulus in 20 degreeC is 4 * 10 <^5> Pa or less, and the storage elastic modulus in 150 degreeC is 1 * 10 <^4> Pa or more. It is preferable that the storage elastic modulus in 150 degreeC of a front surface side adhesive sheet is 9x10 <^3> Pa or less.

It is preferable that the gel fraction of a 2nd adhesive layer is larger than the gel fraction of a 1st adhesive layer. As for the difference of the gel fraction of the adhesive of the 1st adhesive layer, and the gel fraction of the adhesive of a 2nd adhesive layer, 15 weight% or more is preferable. It is preferable that the gel fraction of an adhesive is 55 weight% or less in a 1st adhesive layer. It is preferable that the gel fraction of an adhesive is 75 weight% or more of a 2nd adhesive layer.

It is preferable that the adhesive of a 1st adhesive layer is formed of the adhesive composition containing an acrylic base polymer. It is preferable that the acrylic base polymer of a 1st adhesive layer contains a hydroxyl group containing monomer as a monomer unit. When the base polymer of the first pressure sensitive adhesive layer contains a hydroxy group-containing monomer, cloudiness of the pressure sensitive adhesive layer is suppressed even when exposed to a high temperature, high humidity environment.

It is preferable that the adhesive of a 2nd adhesive layer is formed of the adhesive composition containing an acrylic base polymer. It is preferable that the acrylic base polymer of a 2nd adhesive layer contains a nitrogen containing monomer and / or a carboxy group containing monomer as a monomer unit. When the base polymer of a 2nd adhesive layer contains a nitrogen containing monomer and a carboxyl group-containing monomer, there exists a tendency for the adhesiveness to a front transparent plate and a touch panel to become high.

It is preferable that both a 1st adhesive layer and a 2nd adhesive layer contain a silane coupling agent. Since both of a 1st adhesive layer and a 2nd adhesive layer contain a silane coupling agent, there exists a tendency for the interlayer peeling of a laminated adhesive sheet to be suppressed.

As for the thickness of a 1st adhesive layer, 40 micrometers or more are preferable. As for the thickness of a 2nd adhesive layer, 5 micrometers-70 micrometers are preferable. Ratio d ₁ / d ₂ of the first thickness of the pressure-sensitive adhesive layer d ₁ and the second thickness of the pressure-sensitive adhesive layer ₂ is d, the 2 to 40 is preferred.

The optical film with an adhesive of one embodiment of the present invention is an optical film provided with a double-sided adhesive which further includes a cell-side adhesive sheet on the other side of the optical film.

The optical film provided with the laminated adhesive sheet of this invention and an adhesive is used for formation of the image display apparatus provided with a front transparent plate or a touch panel on the surface of an image display panel. The image display apparatus of this invention is equipped with the optical film with the said adhesive, and the front transparent plate or touch panel on the surface of an image display cell. An optical film and a front transparent plate or a touch panel are bonded together through the said laminated adhesive sheet.

In the laminated pressure sensitive adhesive sheet of the present invention, the second pressure sensitive adhesive layer bonded to the front transparent member has a high storage elastic modulus at a high temperature, and therefore even when outgas is generated from the front transparent member by heating, Retention of bubbles at the bonding interface can be suppressed. Moreover, since the temperature dependence of the storage elastic modulus of the 1st adhesive layer arrange | positioned at the optical film side is large, and it is excellent in level | step difference absorption, mixing of the bubble in step vicinity is suppressed and generation | occurrence | production of the display nonuniformity of an image display apparatus is also suppressed. .

BRIEF DESCRIPTION OF THE DRAWINGS It is typical sectional drawing which shows one form of laminated adhesive sheet.
It is typical sectional drawing which shows one form of the optical film with an adhesive.
It is typical sectional drawing which shows one form of the optical film with a double-sided adhesive.
4 is a cross-sectional view schematically showing one embodiment of an image display device.

1 is a cross-sectional view showing one embodiment of a laminated pressure sensitive adhesive sheet. The laminated adhesive sheet 20 is a laminated body of the 1st adhesive layer 21 and the 2nd adhesive layer 22, and is a double-sided adhesive sheet of the inorganic material which does not have base materials, such as a film, between adhesive layers. In the form shown in FIG. 1, protective sheets 41 and 42 are temporarily attached to each surface of the 1st adhesive layer 21 side and the 2nd adhesive layer 22 side of a laminated adhesive sheet. FIG. 2: is a schematic cross section which shows one form of the optical film 83 with an adhesive with which the laminated adhesive sheet 20 was formed in one surface of the optical film 10 containing a polarizing plate. In the optical film 83 with an adhesive, the surface on the side of the first adhesive layer 21 of the laminated pressure sensitive adhesive sheet 20 is bonded to the optical film 10.

In the formation of the image display apparatus, the laminated adhesive sheet 20 is a front side adhesive sheet for bonding a front side transparent member to the visual recognition side of a polarizing plate. FIG. 4: is a schematic cross section which shows one form of the image display apparatus using the laminated adhesive sheet 20 as a front side adhesive sheet. In the image display apparatus 100, the optical film 10 is arrange | positioned between the front transparent member 70 in which the printing part 76 was formed on the transparent plate 71, and the image display cell 61. As shown in FIG. The optical film 10 and the image display cell 61 are bonded through the cell side adhesive sheet 26, and the optical film 10 and the front transparent member 70 are laminated through the laminated adhesive sheet 20. FIG. Are joined together. As for the laminated adhesive sheet 20, the surface by the side of the 1st adhesive layer 21 is bonded by the optical film 10, and the surface by the side of the 2nd adhesive layer 22 is bonded by the front transparent member 70. As shown in FIG. .

[Front Side Adhesive Sheet]

As mentioned above, the laminated adhesive sheet 20 is a front side adhesive sheet for bonding a front side transparent member to the visual recognition side of a polarizing plate. The laminated pressure sensitive adhesive sheet 20 includes at least two pressure sensitive adhesive layers. The first pressure sensitive adhesive layer 21 is a pressure sensitive adhesive layer for bonding with the optical film 10, and the second pressure sensitive adhesive layer 22 is a pressure sensitive adhesive layer for bonding with the front transparent member. In the optical film provided with the pressure-sensitive adhesive having the laminated pressure-sensitive adhesive sheet 20 formed on the optical film 10, the first pressure-sensitive adhesive layer 21 is disposed in contact with the optical film 10, and the second pressure-sensitive adhesive layer 22 is the optical film. Most spaced apart from (10). When the laminated pressure sensitive adhesive sheet is composed of two layers of the first pressure sensitive adhesive layer 21 and the second pressure sensitive adhesive layer 22, the optical film 53 with the pressure sensitive adhesive is the first pressure sensitive adhesive layer 21 on the optical film 10. And a second pressure sensitive adhesive layer in this order.

The first pressure sensitive adhesive layer 21 disposed in contact with the optical film 10 is composed of a relatively soft pressure sensitive adhesive, and the second pressure sensitive adhesive layer 22 disposed most remotely from the optical film 10 is a relatively hard adhesive. Consists of A hard adhesive is used as the second pressure sensitive adhesive layer 22 formed in contact with the front transparent member at the time of forming the image display device, so that the front transparent member generates an outgas (for example, an acrylic plate or polycarbonate). Even in the case of containing a plastic material such as a plate), the pressure-sensitive adhesive layer can resist the discharge pressure of the outgas, and the retention of bubbles between the pressure-sensitive adhesive sheet and the front transparent member can be suppressed. In addition, since a soft adhesive is used as the first pressure sensitive adhesive layer 21, the overall adhesiveness (fluidity) of the laminated adhesive sheet 20 can be maintained, and the adhesive can enter the vicinity of the printing step of the front transparent member, so that the pressure sensitive adhesive can be placed near the step. It is possible to suppress the mixing of air bubbles. Furthermore, since the overall softness of the laminated pressure sensitive adhesive sheet 20 is maintained, the display unevenness of the peripheral part of the screen due to the printing step can be suppressed.

For example, when the gel fraction of the 1st adhesive layer 21 is smaller than the gel fraction of the 2nd adhesive layer 22, a 1st adhesive layer can be made relatively soft. By having different gel fractions between the first pressure sensitive adhesive layer and the second pressure sensitive adhesive layer, it is possible to give different viscoelastic behavior to both of them, suppressing bubble mixing and suppressing image display unevenness around the printing step, and from the front transparent member. The suppression of bubble retention with respect to the interface due to the outgas of is compatible.

<Characteristics of the first pressure sensitive adhesive layer>

(Save modulus)

As for the 1st adhesive layer 21 formed in the optical film 10 side, the storage elastic modulus G'150 in ₁₅₀ degreeC is 9 * 10 <^3> Pa or less. When the storage elastic modulus at the high temperature of the first pressure sensitive adhesive layer is low, the fluidity at the time of heat bonding by vacuum heating or autoclave is high, and the adhesive easily enters the step vicinity, so that the generation of bubbles in the step difference can be suppressed. . On the other hand, in the heating state at the time of bonding, the film in order to suppress the fumes becomes empty, the pressure-sensitive adhesive from the end surface, the storage elastic modulus at 150 ℃ of the first pressure-sensitive adhesive layer (21) G _'150 is, 3 × 10 ² ㎩ over This is preferred. Claim 1 G _'150 of the pressure-sensitive adhesive layer is more preferably 5 × 10 ² ㎩ to 9 × 10 ³ ㎩.

Similarly, a high fluidity when heated, and also from the viewpoint of suppressing the fumes becomes empty, the pressure-sensitive adhesive from the end surface, a storage modulus at 100 ℃ of the first pressure-sensitive adhesive layer (21) G _'100 is, 8 × 10 ² ㎩ to 1.2 * 10 <^4> Pa is preferable, 9 * 10 <^2> Pa ~ 1 * 10 <^4> Pa is more preferable, and 1 * 10 <^3> Pa ~ 1 * 10 <^4> Pa is further more preferable.

A first pressure-sensitive adhesive storage elastic modulus G _'20 at 20 ℃ of the layer ^{(21), 5 × 10 4} ㎩ to 1 × 10 ⁷ ㎩ are preferred, more preferably 8 × 10 ⁴ ㎩ to 5 × 10 ⁶ ㎩ and 1 × 10 ⁵ kPa to 1 × 10 ⁶ kPa is more preferable. When storage elastic modulus at normal temperature is 5 * 10 <^4> Pa or more, adhesion of an adhesive to the cutting edge etc. when cutting an adhesive sheet and the optical film with an adhesive to a predetermined magnitude | size can be reduced. If storage elastic modulus at normal temperature is 1 * 10 <^7> Pa or less, the adhesiveness in a cut surface, the defect, etc. in the cut surface at the time of cut | disconnecting an optical film with an adhesive sheet or an adhesive to a predetermined magnitude | size can be prevented. Further, if the G _'20 is the range of the first pressure-sensitive adhesive layer can be maintained with the cohesive force necessary for workability and handling properties, it is possible to secure the initial adhesiveness at the time of bonding of the optical film.

A first pressure-sensitive adhesive layer (21) is a storage elastic modulus G 'storage modulus G of from ₂₀ to 150 ℃' G ratio of _{150 '20} / G' ₁₅₀ is more than 20 at 20 ℃. Since the temperature dependence of storage elastic modulus is large, fluidity | liquidity is small at normal temperature, and adhesion | attachment of the adhesive to the cutting blade at the time of a cut, etc. can be suppressed. At the time of heating, since fluidity | liquidity is high and an adhesive easily enters in the vicinity of a printing level | step, mixing of the bubble into the printing level vicinity, and the display unevenness of an image display apparatus can be suppressed. G _'20 / G' ₁₅₀ is preferably at least 25, and preferably at least 30 than this. The upper limit of G _'20 / G' ₁₅₀ is not particularly limited, considering the fluidity during the tack or heat at the time of the bonding at room temperature, 500 and below is preferable, and 300 or less, more preferably, 100 or less, more preferably Do.

In the same point of view, the first, the storage elastic modulus G 'storage modulus G of from ₂₀ to ₁₀₀ ℃' 100 ratio G _'20 / G' ₁₀₀ of is, 18, and 15 or more preferably at 20 ℃ of the pressure-sensitive adhesive layer 21, 300 is more preferable, and 20-100 are more preferable.

In this specification, storage elastic modulus G 'is the temperature increase rate 5 in the range of -50-150 degreeC on the conditions of 1 kW based on the method described in JISK7244-1 "The test method of a plastic-dynamic mechanical property." It is calculated | required by reading the value in predetermined temperature at the time of measuring at ° C / min. The elastic modulus of a material exhibiting viscoelasticity, such as an adhesive, is represented by the storage modulus G 'and the loss modulus G ". In general, the loss modulus G" is an index indicating the degree of viscosity, while the storage modulus G' is a measure of hardness. Marking is used as an indicator.

(Residual stress)

0.1-6 N / cm <2> is preferable, as for the residual stress in 20 degreeC of a 1st adhesive layer, 0.2-5 N / cm <2> is more preferable, 0.3-4 N / cm <2> is further more preferable. If the residual stress is within the above range, the adhesive can be provided with step-following properties, thereby suppressing bubbles and display unevenness, while suppressing sticking of the adhesive from the end face and adhesion of the adhesive to the cutting blade at the time of cutting. can do.

Residual stress in this specification is a residual stress after 180 second measured by the tensile stress relaxation test of 25 degreeC and 300% of deformation conditions. Specifically, the residual stress is a stress (tensile stress) after the elapse of 180 seconds after straining by a tensile tester until it is distorted at a tensile rate of 200 mm / minute to 300% (four times the original length). The residual stress has a high correlation with the storage elastic modulus, and the higher the storage elastic modulus, the larger the residual stress tends to be. When the composition of the base polymer of an adhesive is equal, when a gel fraction (crosslinking degree) becomes large, there exists a tendency for residual stress to increase linearly with it.

(Gel fraction)

Although the optimum value of the gel fraction of a pressure-sensitive adhesive (a ratio of a solvent insoluble component) varies depending on the composition of the pressure-sensitive adhesive and the like, the gel fraction of the first pressure-sensitive adhesive layer 21 is preferably 55% or less from the viewpoint of providing step absorbency. 52% or less are more preferable, and 50% or less is more preferable. Although the minimum of the gel fraction of the 1st adhesive layer 21 is not specifically limited, 15% or more from a viewpoint of suppressing sticking of the adhesive from an end surface, adhesion of the adhesive to the cutting blade at the time of a cut, etc. It is preferable, 20% or more is more preferable, and 25% or more is more preferable.

The gel fraction of an adhesive can be calculated | required as an insoluble content with respect to a solvent, Specifically, the weight fraction with respect to the sample before immersion of the insoluble component after immersing an adhesive (adhesive layer or an adhesive sheet) in a solvent for 7 days at 23 degreeC. It is calculated | required as (unit: weight%). When the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive, ethyl acetate is used as the solvent. In general, the gel fraction of the polymer is the same as the degree of crosslinking, and the more crosslinked portions in the polymer, the larger the gel fraction and the higher the storage modulus G 'and the residual stress.

(thickness)

The thickness d ₁ of the first pressure sensitive adhesive layer 21 is preferably 40 μm or more. First thickness d ₁ of the pressure-sensitive adhesive layer is more than 50㎛ the more preferable, and at least 60㎛ more preferably, at least 70㎛ and particularly preferred, at least 80㎛ most preferred. By increasing the thickness of the first pressure sensitive adhesive layer, the fluidity of the laminated pressure sensitive adhesive sheet at the time of heating is increased, and mixing of bubbles in the vicinity of a printing step can be suppressed. In addition, by increasing the thickness of the first pressure-sensitive adhesive layer, the level difference absorbency of the pressure-sensitive adhesive sheet increases, so that display unevenness of the image display device can be suppressed.

Although the upper limit of the thickness d ₁ of the 1st adhesive layer 21 is not specifically limited, From a viewpoint of productivity of an adhesive sheet, the prevention of protruding from an end surface, etc., 500 micrometers or less are preferable and 400 micrometers or less are more preferable. Preferably, 300 micrometers or less are more preferable, and 250 micrometers or less are especially preferable.

<Physical properties of the second pressure sensitive adhesive layer>

(Save modulus)

The 2nd adhesive layer 22 arrange | positioned in the position furthest from the optical film 10 is an adhesive layer for bonding with a front transparent member. The storage elastic modulus at 150 degrees C of the 2nd adhesive layer 22 is 1 * 10 <^4> Pa or more. When the storage elastic modulus at the high temperature of the second pressure sensitive adhesive layer is high, even when outgas is released from the front transparent member, the second pressure sensitive adhesive layer can resist the discharge pressure of the outgas, and the pressure sensitive adhesive sheet and the front transparent member Retention of bubbles at the interface with can be suppressed. On the other hand, if the storage elastic modulus at the high temperature of the second pressure sensitive adhesive layer is excessively high, even when the storage elastic modulus of the first pressure sensitive adhesive layer is low, the introduction of the adhesive near the printing step is inhibited and bubbles are generated or displayed on the image display device. Unevenness may occur. Accordingly, the second storage elastic modulus G _'150 is less than 1 × 10 ⁶ ㎩ at 150 ℃ of the pressure-sensitive adhesive layer 22 is preferred. Claim 2 G _'150 of the pressure-sensitive adhesive layer is, 1 × 10 ⁴ ㎩ to 8 × 10 ⁵ ㎩ more preferably, 3 × 10 ⁴ to 5 × 10 ㎩ is more preferably ⁵ ㎩.

Similarly, the storage elastic modulus G ' ₁₀₀ at 100 ° C of the second pressure sensitive adhesive layer 22 is suppressed from the viewpoint of suppressing the outgas retention to the interface during heating and suppressing bubbles and display irregularities in the vicinity of the printing step. , 1 × 10 ⁴ kPa to 1 × 10 ⁶ kPa is preferable, 3 × 10 ⁴ kPa to 9 × 10 ⁵ kPa is more preferable, and 4 × 10 ⁴ kPa to 6 × 10 ⁵ kPa is more preferable.

The second pressure-sensitive adhesive layer having a G _'20 tends to be too high, bubbles are likely to be mixed in the vicinity of the bonding step the initial stage. In addition, the second case ₂₀ the G 'of the adhesive layer is too high and can not absorb the stress due to the step difference of the front transparent member in the second pressure-sensitive adhesive layer tends to have display unevenness occurs. Therefore, the second pressure-sensitive adhesive layer 22, the storage elastic modulus G _'20 is more preferably 1 × 10 ⁶ ㎩ than or less preferably, 8 × 10 ⁵ ㎩ at 20 ℃ of, and not more than 6 × 10 ⁵ ㎩ More preferred.

From the viewpoint of reducing the adhesion of the pressure-sensitive adhesive for the equipped with a pressure-sensitive adhesive sheet or pressure-sensitive adhesive optical film or the like cutting edge at the time a predetermined cut into size, a and more than G _'20 is 5 × 10 ⁴ ㎩ the second pressure-sensitive adhesive layer preferably, 8 × 10 ⁴ Pa or more is more preferable, and 1 * 10 ⁵ Pa or more is more preferable.

The second pressure-sensitive adhesive layer 22, that "the storage modulus G of from ₂₀ to ₁₅₀ ℃ '150 ratio G' ₂₀ / G _'150 is less than or equal to 20, the storage elastic modulus G of from 20 ℃ is preferable, more preferably 15 or less It is more preferable that it is 10 or less. The temperature dependence of the storage elastic modulus of the second adhesive layer is small, G _'20 / G' pressure-sensitive adhesive of the by the value of ₁₅₀ small, because even if any at the time of room temperature, and heating is small, the fluidity of the adhesive, cut at the time of cutting edge etc. The adhesion of the particles can be suppressed, and the retention of bubbles at the bonding interface can be suppressed even when outgas is generated from the entire surface transparent member during heating. The lower limit of G _'20 / G' ₁₅₀ is not particularly limited, generally is greater than 1, preferably 2 or more. By the gel fraction of the second pressure-sensitive adhesive layer significantly, G tends to reduce the _'20 / G' _150.

In such aspect, the second, the storage modulus G _'20 to the storage elastic modulus G of from ₁₀₀ ℃' 100 ratio G _'20 / G' ₁₀₀ of at 20 ℃ is 15 or less are preferred, and 10 of the pressure-sensitive adhesive layer 22, The following is more preferable, and 8 or less are more preferable.

Claim 2 G of the pressure-sensitive adhesive layer 22 is preferably greater than _'150, claim 1 G of the pressure-sensitive adhesive layer 21, _150. The second pressure-sensitive adhesive G of the layer is more than three times that of _'150, a first pressure-sensitive adhesive G of layer _"150, and preferably, two, and more preferably 5 times or more, it is more than 7 times more preferable, 10 times or more is particularly preferred. Likewise, of the second pressure-sensitive adhesive layer G is twice or more of the _'100, a first pressure-sensitive adhesive G of layer _"100, and preferably, and more than three times more preferred, particularly preferably 5 times or more is more preferred, and more than eight times the Do.

The G _'20 / G' ₁₅₀ of the first pressure-sensitive adhesive layer 21, and the second is preferably greater G _'20 / G' ₁₅₀ of all of the pressure-sensitive adhesive layer 22. Claim 1 G _'20 / G' ₁₅₀ of the pressure-sensitive adhesive layer 21, a second adhesive layer 22 in the G _'20 / G' at least three times that of ₁₅₀ is preferred, and more preferred at least 5x, 7x The above is more preferable, and 10 times or more is especially preferable. In addition, the 1 G _'20 / G' ₁₀₀ of the pressure-sensitive adhesive layer 21, and the second is preferably greater than the G _'20 / G' ₁₀₀ of the pressure-sensitive adhesive layer 22. Claim 1 G _'20 / G' ₁₀₀ of the pressure-sensitive adhesive layer 21, the second, and the pressure-sensitive adhesive less than two times the layer 22 on the G _'20 / G' ₁₀₀ is preferable, more than four times that of a preferred, 6x The above is more preferable, and 8 times or more is especially preferable. A first ratio of the pressure-sensitive adhesive layer and the second adhesive G _'20 / G' rain and ₁₅₀ of layer G _'20 / G' ₁₀₀ is an indicator of the differences in the temperature dependence of the storage elastic modulus of these pressure-sensitive adhesive layer, the larger the ratio This indicates that the difference in viscoelastic behavior is large.

The laminated pressure sensitive adhesive sheet of the present invention is different in temperature dependence of storage elastic modulus, and a plurality of pressure sensitive adhesive layers having a large difference in storage elastic modulus are laminated in a high temperature state, thereby increasing the overall fluidity of the pressure sensitive adhesive sheet to have print step absorbency, Retention of outgas to the bonding interface can be suppressed.

(Residual stress)

1-30 N / cm <2> is preferable, as for the residual stress in 25 degreeC of a 2nd adhesive layer, 3-20 N / cm <2> is more preferable, 5-15 N / cm <2> is further more preferable. Moreover, it is preferable that the residual stress of a 2nd adhesive layer is larger than the residual stress of a 1st adhesive layer. When the residual stress of the second pressure sensitive adhesive layer is large, the retention of outgas to the bonding interface can be suppressed.

It is preferable that the residual stress of a 2nd adhesive layer is larger than the residual stress of a 1st adhesive layer. Even if the storage modulus is equal, the larger the residual stress, the harder the pressure-sensitive adhesive is and the greater the drag force against the force from the outside. Therefore, by increasing the residual stress of the second pressure sensitive adhesive layer, the effect of suppressing the retention of outgas generated from the front transparent member is increased. 1.5 times or more of the residual stress of a 1st adhesive layer is preferable, as for the residual stress of a 2nd adhesive layer, 2 times or more are more preferable, and 2.5 times or more are more preferable.

(Gel fraction)

It is preferable that the gel fraction of the 2nd adhesive layer 22 is larger than the gel fraction of the 1st adhesive layer. It is preferable that the gel fraction of a 2nd adhesive layer is 15% or more larger than the gel fraction of a 1st adhesive layer, It is preferable that it is 20% or more, It is more preferable that it is 25% or more, It is especially preferable that it is 30% or more. . 75% or more is preferable, as for the gel fraction of a 2nd adhesive layer, 80% or more is more preferable, and 85% or more is more preferable. 99% or less is preferable and, as for the gel fraction of a 2nd adhesive layer, 95% or less is more preferable.

By making the gel fraction of a 2nd adhesive layer relatively large, retention of outgas with respect to a joining interface can be suppressed. Moreover, peeling of the adhesive from the front transparent member in a high temperature environment is suppressed as the gel fraction of a 2nd adhesive layer is 75% or more. If the gel fraction is 99% or less, appropriate cohesion and flexibility are obtained, and the initial adhesiveness is increased.

(thickness)

The thickness d ₂ of the second pressure-sensitive adhesive layer 22 is at least 5㎛ and preferred, and more preferably more than 10㎛, at least 15㎛ is more preferred. By contacting the front transparent member side and increasing the thickness of the relatively hard second pressure sensitive adhesive layer, even when outgas is emitted from the front transparent member, the second pressure sensitive adhesive layer can resist the discharge pressure of the outgas, Retention of bubbles at the interface between the pressure-sensitive adhesive sheet and the front transparent member can be suppressed.

70 micrometers or less are preferable, as for the thickness of a 2nd adhesive layer, 50 micrometers or less are more preferable, 40 micrometers or less are more preferable. In addition, the thickness d ₂ of the second pressure sensitive adhesive layer 22 is preferably smaller than the thickness d ₁ of the first pressure sensitive adhesive layer 21. First thickness ratio d ₁ / d ₂ of d ₂ of the pressure-sensitive adhesive layer 21, thickness d ₁ and a second pressure-sensitive adhesive layer 22 of is 2 to 50, more preferably from 3 to 30 and 4 to 20 This is more preferable.

By increasing the thickness of the first pressure sensitive adhesive layer relatively larger than the second pressure sensitive adhesive layer, the overall viscoelastic behavior of the laminated pressure sensitive adhesive sheet 20 in which the first pressure sensitive adhesive layer 21 and the second pressure sensitive adhesive layer 22 are laminated is the first pressure sensitive adhesive. The viscoelasticity of the layers becomes dominant. Therefore, the level | step difference absorbency of a laminated adhesive sheet becomes high, and mixing of a bubble to the printing level vicinity, and the display nonuniformity of an image display apparatus can be suppressed. On the other hand, the characteristic of the 2nd adhesive layer which contact | connects a front side transparent member becomes dominant in suppressing the release of outgas from a front side transparent member. In the laminated pressure sensitive adhesive sheet of the present invention, a hard adhesive is used as the second pressure sensitive adhesive layer, so that even when the front transparent member includes a material generating outgas, it is possible to resist the discharge pressure of the outgas, and The retention of bubbles between the front transparent members can be suppressed.

<Characteristics of Laminated Adhesive Sheets>

In the laminated adhesive sheet 20, the 1st adhesive layer 21 is arrange | positioned at the bonding surface with an optical film, and the 2nd adhesive layer 22 is arrange | positioned at the bonding surface with a front transparent member. The laminated pressure sensitive adhesive sheet may be a laminate of these two layers, or may have another pressure sensitive adhesive layer between the first pressure sensitive adhesive layer and the second pressure sensitive adhesive layer.

(Save modulus)

The storage modulus G _'150 at 150 ℃ of the multilayer pressure-sensitive adhesive sheet, 2 × 10 ⁴ ㎩ and less are preferred, more preferably less than ^{1 × 10 4 ㎩, 9 ×} 10 more preferably less than ³ ㎩. If the laminate adhesive sheet G _'150 is the above-described range, the bubbles are generated in the vicinity of the step or, it is possible to suppress the occurrence of display non-uniformity on the image display device. Film from the viewpoint of suppressing the fumes becomes empty, the pressure-sensitive adhesive from the end surface, the storage modulus G _'150 at 150 ℃ of the multilayer pressure-sensitive adhesive sheet, at least 5 × 10 ² ㎩ are preferred, at least 8 × 10 ² ㎩ more preferably Do.

Similarly, a high fluidity when heated, and also from the viewpoint of suppressing the fumes becomes empty, the pressure-sensitive adhesive from the end surface, the storage modulus G _'100 at 100 ℃ of the multilayer pressure-sensitive adhesive sheet ^{(20), 5 × 10 2} ㎩ to 3 × 10 ⁴ kPa is preferable, 8 × 10 ² kPa to 2 × 10 ⁴ kPa is more preferable, and 1 × 10 ³ kPa to 1.5 × 10 ⁴ kPa is more preferable.

Storage elastic modulus G of the laminated adhesive sheet 20 at 20 degrees C from a viewpoint of suppressing adhesion | attachment of an adhesive to the cutting edge, etc. when cutting an adhesive film or an optical film with an adhesive to a predetermined magnitude | size, or an adhesive gap and a defect. _"20, 5 × 10 ⁴ ㎩ to 1 × 10 ⁷ ㎩ are preferred, 8 × 10 ⁴ ㎩ to 5 × 10 ⁶ ㎩ is more preferred, and even more preferably 1 × 10 ⁵ ㎩ to 1 × 10 ⁶ ㎩ .

20 ℃ storage modulus G 'storage modulus at ₂₀ and 150 ℃ G' ₁₅₀ ratio G _'20 / G' ₁₅₀ of in the laminated pressure-sensitive adhesive sheet 20, 20 and above are preferred, at least 25 more preferred, 30 or more are more preferable. By large temperature dependence of the storage elastic modulus of a laminated adhesive sheet, fluidity | liquidity is small at normal temperature, and adhesion | attachment of the adhesive to the cutting blade at the time of a cut, etc. can be suppressed. At the time of heating, since fluidity is high and an adhesive enters easily in the vicinity of a printing level | step, mixing of the bubble into the printing level vicinity, and the display nonuniformity of an image display apparatus can be suppressed. The upper limit of G _'20 / G' ₁₅₀ is not particularly limited, considering the fluidity during the tack or heat at the time of the bonding at room temperature, 500 and below is preferable, and 300 or less, more preferably, 100 or less, more preferably Do.

In the same point of view, of the laminated adhesive sheet 20, and the storage elastic modulus G is "storage modulus G of from ₂₀ to ₁₀₀ ℃ '100 ratio G' ₂₀ / G _'100 of 10 or more at 20 ℃ preferably, from 15 to 300 is more preferable, and 20-100 are more preferable.

As described above, by increasing the thickness of the first pressure sensitive adhesive layer 21 relative to the second pressure sensitive adhesive layer 22, the overall viscoelastic behavior of the laminated pressure sensitive adhesive sheet 20 becomes dominant because the viscoelasticity of the first pressure sensitive adhesive layer is dominant. , it can increase the temperature dependence of the storage modulus of the multilayer pressure-sensitive adhesive sheet, and adjusted in the G _'20 / G' ₁₅₀ and G _'20 / G' ₁₀₀ to the range of values.

(thickness)

From the viewpoint of increasing the level difference absorbency by the laminated pressure sensitive adhesive sheet and suppressing display unevenness of the image display device, the thickness of the laminated pressure sensitive adhesive sheet 20 is preferably 55 μm or more, more preferably 100 μm or more, and 130 μm or more This is more preferable and 150 micrometers or more are especially preferable. On the other hand, from the viewpoint of productivity of the pressure sensitive adhesive sheet, prevention of protruding from the end face, etc., the thickness of the laminated pressure sensitive adhesive sheet is preferably 550 µm or less, more preferably 450 µm or less, still more preferably 350 µm or less, 300 micrometers or less are especially preferable.

As described above, the laminated pressure sensitive adhesive sheet may have another pressure sensitive adhesive layer between the first pressure sensitive adhesive layer and the second pressure sensitive adhesive layer. Although the composition and the characteristic of the adhesive layer arrange | positioned between a 1st adhesive layer and a 2nd adhesive layer are not specifically limited, It is preferable that the whole characteristic of a laminated adhesive sheet is the said range. It is preferable that a laminated adhesive sheet is a laminated structure which consists of two layers of a 1st adhesive layer and a 2nd adhesive layer from a viewpoint of the productivity of a laminated adhesive sheet, and the ease of property control.

<Composition of adhesive>

The pressure-sensitive adhesive constituting the first pressure-sensitive adhesive layer 21 and the second pressure-sensitive adhesive layer 22 is not particularly limited as long as the pressure-sensitive adhesive satisfies the above characteristics. Acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, Polymers such as polyvinyl ether, vinyl acetate / vinyl chloride copolymer, modified polyolefin, epoxy type, fluorine type, rubber type such as natural rubber and synthetic rubber can be appropriately selected and used. Since the 1st adhesive layer and the 2nd adhesive layer are adhesives used for an image display apparatus, what is excellent in optical transparency is used preferably. Specifically, the first adhesive layer and the second adhesive layer each preferably have a haze of 1.0% or less and a total light transmittance of 90% or more.

As an adhesive excellent in optical transparency and adhesiveness, the acrylic adhesive which uses an acrylic polymer as a base polymer is used preferably. It is preferable that content of the acrylic base polymer with respect to solid content whole quantity of an adhesive composition is 50 weight% or more, It is more preferable that it is 70 weight% or more, It is further more preferable that an acrylic adhesive is 80 weight% or more.

As an acryl-type polymer, what uses a monomer unit of a (meth) acrylic-acid alkylester as a main skeleton is used suitably. In addition, in this specification, "(meth) acryl" means an acryl and / or methacryl.

As (meth) acrylic-acid alkylester, the (meth) acrylic-acid alkylester whose carbon number of an alkyl group is 1-20 is used suitably. For example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, and pentyl (meth) acrylate Isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, ( Nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, isotridodecyl (meth) acrylate Tetradecyl acrylate, Isotetradecyl (meth) acrylate, Pentadecyl (meth) acrylate, Cetyl (meth) acrylate, Heptadecyl (meth) acrylate, Octadecyl (meth) acrylate, Isooctadecyl (meth) acrylate, (meth Nonadecyl acrylate, (meth) arc And the like isostearyl acid, (meth) acrylic acid alkyl.

It is preferable that content of the said (meth) acrylic-acid alkylester is 40 weight% or more with respect to the monomer component whole quantity which comprises a base polymer, 50 weight% or more is more preferable, and 60 weight% or more is more preferable.

In order to satisfy the various characteristics mentioned above, as an acrylic base polymer of a 1st adhesive layer and a 2nd adhesive layer, the copolymer of several (meth) acrylic-acid alkylester is used preferably. In the copolymer, the arrangement of the structural monomer units may be random or may be a block.

The alkyl group of the (meth) acrylic acid alkyl ester may have a branch. Among the monomers in the above examples, examples of the branched alkyl (meth) acrylic acid esters include 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate and isomethacrylate (meth) acrylate. Tetradecyl, isooctadecyl (meth) acrylate, isostearyl (meth) acrylate, etc. are used suitably. Moreover, branched alkyl (meth) acrylic acid ester can also use 2 or more types together.

It is preferable that an acrylic base polymer contains the acryl-type monomer unit which has a crosslinkable functional group as a copolymerization component. When a base polymer has a crosslinkable functional group, the gel fraction of an adhesive by thermal crosslinking, photocuring, etc. of a base polymer can be raised easily. As an acryl-type monomer which has a crosslinkable functional group, a hydroxyl group containing monomer and a carboxy group containing monomer are mentioned.

Especially, when a base polymer contains a hydroxyl group containing monomer and a nitrogen containing monomer as a copolymerization component, there exists a tendency for the cloudiness of the adhesive in high temperature, high humidity environment to be suppressed, and the adhesive with high transparency is obtained. In the laminated pressure sensitive adhesive sheet 20, at least one of the first pressure sensitive adhesive layer 21 and the second pressure sensitive adhesive layer 22 is a copolymerized component of a base polymer, and at least one of a hydroxy group-containing monomer and a nitrogen-containing monomer is used. It is preferable to contain. Especially, from a viewpoint of suppressing the cloudiness of a laminated adhesive sheet in a high temperature, high humidity environment, a relatively large 1st adhesive layer contains at least one of a hydroxyl group containing monomer and a nitrogen containing monomer as a copolymerization component of a base polymer. It is preferable that both of the first pressure sensitive adhesive layer and the second pressure sensitive adhesive layer contain at least one of a hydroxy group-containing monomer and a nitrogen-containing monomer as a copolymerization component of the base polymer. As for the sum total of content of a hydroxy-group containing monomer and a nitrogen-containing monomer, 5-50 weight% is preferable with respect to the structural monomer unit whole quantity of a base polymer, 7-45 weight% is more preferable, 10-40 weight% is still more preferable. .

As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and (meth) acrylic acid -Hydroxyoctyl, (meth) acrylic acid 10-hydroxydecyl, (meth) acrylic acid 12-hydroxylauryl, (4-hydroxymethylcyclohexyl) -methyl (meth) acrylate, etc. are mentioned.

As the nitrogen-containing monomer, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyl oxazole, vinyl mor Vinyl-based monomers such as polyline, (meth) acryloyl morpholine, N-vinylcarboxylic acid amides, and N-vinyl caprolactam, and cyano group-containing monomers such as acrylonitrile and methacrylonitrile. have. Especially, N-vinylpyrrolidone and (meth) acryloyl morpholine are used preferably.

When a base polymer contains a carboxyl group-containing monomer and a nitrogen-containing monomer as a copolymerization component, the cohesion force of an adhesive improves and even when a gel fraction is high, there exists a tendency for the adhesiveness to the to-be-adhered body of an adhesive sheet to become high. Therefore, it is preferable that the 2nd adhesive layer 22 contains at least any one of a carboxyl group-containing monomer and a nitrogen-containing monomer as a copolymerization component of a base polymer. 2-20 weight% is preferable with respect to the constituent monomer unit whole quantity of a base polymer, and, as for content of a carboxyl group-containing monomeric unit, 3-15 weight% is more preferable. 3-40 weight% is preferable with respect to the structural monomer unit whole quantity of a base polymer, as for content of a nitrogen-containing monomer unit, 5-30 weight% is more preferable, and its 7-25 weight% is further more preferable.

Examples of the carboxyl group-containing monomers include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid. Especially, acrylic acid is used preferably.

As the copolymerized monomer component of the base polymer, an acid anhydride group-containing monomer, a caprolactone adduct of acrylic acid, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, and the like may be used in addition to the above.

The polyfunctional monomer component may be contained in the monomer component which forms an acryl-type polymer. By having a polyfunctional monomer as a copolymerization monomer component, there exists a tendency for the gel fraction of an adhesive to become high. A polyfunctional monomer is a monomer which has at least two polymerizable functional groups which have unsaturated double bonds, such as a (meth) acryloyl group.

By using a polyfunctional monomer, a branch point is introduce | transduced into a base polymer and it exists in the tendency for the gel fraction of an adhesive to become high. Moreover, with the increase of the usage-amount of a polyfunctional monomer, there exists a tendency for the gel fraction of an adhesive to become high. Although the usage-amount of a polyfunctional monomer changes with the molecular weight, the number of functional groups, etc., 3 weight% or less is preferable with respect to all the monomer components which form a (meth) acrylic-type polymer, 2 weight% or less is more preferable, 1 weight% The following is more preferable. When the usage-amount of a polyfunctional monomer exceeds 3 weight%, the storage elastic modulus of an adhesive will become large excessively, and it exists in the tendency for the bubble and display nonuniformity to occur in the vicinity of the step part of a front transparent member to occur easily.

The said acrylic base polymer can be prepared by well-known polymerization methods, such as solution polymerization, UV polymerization, block polymerization, and emulsion polymerization. In view of transparency, water resistance, cost, and the like of the pressure-sensitive adhesive, a solution polymerization method or an active energy ray polymerization method (for example, UV polymerization) is preferable. Generally as a solvent of solution polymerization, ethyl acetate, toluene, etc. are used.

At the time of preparation of an acryl-type polymer, you may use superposition | polymerization initiators, such as a photoinitiator and a thermal polymerization initiator, according to the kind of polymerization reaction. The photopolymerization initiator is not particularly limited as long as it initiates photopolymerization, and examples thereof include benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ketol photopolymerization initiators, aromatic sulfonyl chloride photopolymerization initiators, and photoactive oxime photopolymerization initiators. , Benzoin photopolymerization initiator, benzyl photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, thioxanthone photopolymerization initiator, acylphosphine oxide photopolymerization initiator and the like can be used. As the thermal polymerization initiator, for example, an azo initiator, a peroxide initiator, a redox initiator (eg, a combination of persulfate and sodium hydrogen sulfite, a combination of peroxide and sodium ascorbate) Can be used.

In order to adjust the molecular weight of a base polymer, a chain transfer agent may be used. The chain transfer agent can receive radicals from the growing polymer chain to stop elongation of the polymer, and the chain transfer agent which receives radicals can attack the monomer to start polymerization again. Therefore, by using a chain transfer agent, the increase of the molecular weight of a base polymer is suppressed without reducing the radical concentration in a reaction system, and the adhesive sheet with small residual stress can be obtained. As the chain transfer agent, for example, α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, thioglycolic acid 2-ethylhexyl, 2,3-dimercapto Thiols, such as -1-propanol, are used suitably.

When a polyfunctional monomer other than the monofunctional monomer is used as the monomer component for forming the acrylic polymer, first, the monofunctional monomer is polymerized to form a low polymer prepolymer composition (prepolymerization), and then the syrup of the prepolymer composition is used. You may add a functional monomer and superpose | polymerize (postpolymerize) a prepolymer and a polyfunctional monomer. Thus, by performing prepolymerization of a prepolymer, the branching point resulting from a polyfunctional monomer component can be introduce | transduced uniformly in a base polymer. Moreover, after apply | coating the mixture (adhesive composition) of a prepolymer composition and the unpolymerized monomer component on a base material, you may post-polymerize on a base material and form an adhesive sheet. Since the prepolymer composition is excellent in applicability at low viscosity, according to the method of performing post-polymerization on the substrate after applying the pressure-sensitive adhesive composition, which is a mixture of the prepolymer composition and the unpolymerized monomer, the productivity of the pressure-sensitive adhesive sheet increases, and the pressure-sensitive adhesive sheet The thickness of can be made uniform.

A prepolymer composition can be prepared by carrying out partial polymerization (prepolymerization) of the composition (called "composition for forming a prepolymer") which mixed the monomer component which comprises an acrylic base polymer, and a polymerization initiator, for example. Moreover, it is preferable that the said monomer component in the composition for prepolymer formation is monofunctional monomer components, such as an alkyl ester (meth) acrylate and a polar group containing monomer, among the monomer components which comprise an acrylic polymer. In addition, the monomer component for prepolymer formation may contain not only a monofunctional monomer but a polyfunctional monomer. For example, one part of the polyfunctional monomer component used as a raw material of a base polymer may be contained in the composition for prepolymer formation, and the remainder of a polyfunctional monomer component may be added to a postpolymerization after superposition | polymerization.

In addition to a monomer component and a polymerization initiator, the composition for prepolymer formation may contain the chain transfer agent etc. as needed. Although the polymerization method of the composition for prepolymer formation is not specifically limited, From a viewpoint which adjusts reaction time and makes the molecular weight (polymerization rate) of a prepolymer into a desired range, superposition | polymerization by actinic irradiation, such as UV light, is preferable. The polymerization initiator and chain transfer agent used for prepolymerization are not specifically limited, For example, the photoinitiator and chain transfer agent mentioned above can be used.

Although the polymerization rate of a prepolymer is not specifically limited, From a viewpoint of making it suitable viscosity for application | coating on a base material, 3-50 weight% is preferable and 5-40 weight% is more preferable. The polymerization rate of a prepolymer can be adjusted to a desired range by adjusting the kind, usage-amount of a photoinitiator, irradiation intensity, irradiation time, etc. of active light, such as UV light.

The prepolymer composition is mixed with other monomer components constituting the acrylic base polymer and, if necessary, a polymerization initiator, a chain transfer agent, a silane coupling agent, a crosslinking agent and the like to form an adhesive composition. It is preferable that the monomer component added at the time of postpolymerization is a polyfunctional monomer. In addition, the monomer component at the time of postpolymerization may contain the monofunctional monomer other than a polyfunctional monomer.

The photoinitiator and chain transfer agent used for post-polymerization are not specifically limited, For example, the photoinitiator and chain transfer agent mentioned above can be used. When the polymerization initiator at the time of prepolymerization is not deactivated and remains in a prepolymer composition, addition of the polymerization initiator for postpolymerization can be skipped.

The crosslinked structure may be introduced into the base polymer of the pressure-sensitive adhesive by the crosslinking agent. Formation of a crosslinked structure is performed by adding a crosslinking agent, for example after prepolymerization or after superposition | polymerization of a base polymer. As a crosslinking agent, what is generally used, such as an isocyanate type crosslinking agent, an epoxy type crosslinking agent, an oxazoline type crosslinking agent, an aziridine type crosslinking agent, a carbodiimide type crosslinking agent, a metal chelate type crosslinking agent, can be used.

Content of a crosslinking agent is the range of 0-5 weight part normally with respect to 100 weight part of acrylic base polymers, Preferably it is 0-3 weight part. When there is too much content of a crosslinking agent, the gel fraction of an adhesive may increase excessively and it may cause mixing of bubbles and display nonuniformity in the vicinity of a printing step.

When a crosslinking agent is contained in an adhesive composition, it is preferable that the crosslinking process by heating is performed before bonding with a to-be-adhered body, and a crosslinked structure is formed. Although heating temperature and heating time in a crosslinking process are suitably set according to the kind of crosslinking agent to be used, bridge | crosslinking is normally performed by heating for about 1 minute-about 7 days in 20 degreeC-160 degreeC.

The molecular weight of the base polymer is suitably adjusted so that various properties, such as an elasticity modulus, fall in the range mentioned above. It is preferable that the weight average molecular weight of polystyrene conversion is about 50,000-1 million, and, as for the base polymer of a 1st adhesive layer, the range of 100,000-1 million is more preferable. It is preferable that the weight average molecular weight of polystyrene conversion is about 500,000-5 million, and, as for the base polymer of a 2nd adhesive layer, the range of 800,000-4 million is more preferable. Moreover, it is preferable that the weight average molecular weight of the base polymer of a 2nd adhesive layer is larger than the weight average molecular weight of the base polymer of a 1st adhesive layer.

It is preferable that both a 1st adhesive layer and a 2nd adhesive layer contain a silane coupling agent in an adhesive composition. Since both a 1st adhesive layer and a 2nd adhesive layer contain a silane coupling agent, the adhesive force in the interface of an adhesive layer becomes high, and the interlayer peeling in the adhesive interface of a laminated adhesive sheet is suppressed. A silane coupling agent can be used individually by 1 type or in combination of 2 or more types. 0.01-5 weight part is preferable with respect to 100 weight part of acrylic base polymers, as for content of the silane coupling agent in an adhesive, 0.05-2 weight part is more preferable, 0.1-1 weight part is more preferable.

You may add a tackifier to an adhesive composition as needed. Examples of the tackifier include terpene tackifiers, styrene tackifiers, phenolic tackifiers, rosin tackifiers, epoxy tackifiers, dicyclopentadiene tackifiers, and polyamides. A tackifier, a ketone tackifier, an elastomer tackifier, etc. can be used.

In addition to the components of the above examples, additives such as plasticizers, softeners, deterioration agents, fillers, colorants, ultraviolet absorbers, antioxidants, surfactants, and antistatic agents may be added to the pressure-sensitive adhesive composition within a range that does not impair the properties of the pressure-sensitive adhesive. .

<Formation of Adhesive Layer>

Various methods are used as a formation method of an adhesive layer. Specifically, for example, by roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, die coater, etc. The extrusion coating method etc. are mentioned. Among these, it is preferable to use a die coater, and it is more preferable to use the die coater which uses a fountain die and a slot die especially.

When the base polymer of an adhesive composition is a solution polymerization polymer, it is preferable to dry a solvent after application | coating. As a drying method, an appropriate method can be suitably adopted according to the objective. The heat drying temperature is preferably 40 ° C to 200 ° C, more preferably 50 ° C to 180 ° C, and particularly preferably 70 ° C to 170 ° C. The drying time may suitably be employed. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, and particularly preferably 10 seconds to 10 minutes.

When an adhesive composition contains a crosslinking agent, crosslinking by heating may be performed after application | coating to a base material. Although heating temperature and a heat time are suitably set according to the kind of crosslinking agent to be used, bridge | crosslinking is normally performed by heating for about 1 minute-about 7 days in 20 degreeC-160 degreeC. The heating for drying the adhesive after application may serve as heating for crosslinking.

On an adhesive layer, a protective sheet is adhesively peeled as needed. The protective sheet is used for the purpose of protecting the exposed surface of the adhesive until the adhesive is used for bonding to the adherend. You may use the base material used at the time of formation (application) of an adhesive layer as a protective sheet of an adhesive layer.

As a constituent material of a protective sheet, plastic films, such as polyethylene, a polypropylene, a polyethylene terephthalate, and a polyester film, are used preferably. The thickness of a protective sheet is 5-200 micrometers normally, Preferably it is about 10-150 micrometers. The protective sheet is antistatic by antistatic agents such as a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent and release treatment and antifouling treatment by silica powder, coating type, kneading insertion type, and deposition type. The process may be performed. By peeling off the surface of a protective sheet especially, the peelability from an adhesive can be improved more at the time of practical use.

The lamination | stacking method of a 1st adhesive layer and a 2nd adhesive layer is not specifically limited. After forming each of the 1st adhesive layer and the 2nd adhesive layer individually by an adhesive sheet, you may overlap both, and after forming one adhesive layer first as an adhesive sheet, after coating the other adhesive layer on it, laminated adhesive sheet You can also do Moreover, you may form a laminated adhesive sheet by coextrusion of the composition for 1st adhesive layer formation and the composition for 2nd adhesive layer formation.

[Optical Film with Adhesive]

As mentioned above, the laminated adhesive sheet 20 of this invention is a front side adhesive sheet for bonding a front side transparent member to the visual recognition side of a polarizing plate. By forming the laminated adhesive sheet 20 on the optical film 10 containing a polarizing plate, it can be used as an optical film with an adhesive. As shown in FIG. 2, in the optical film with an adhesive, the 1st adhesive layer 21 side is formed in the optical film 10 side.

<Optical film>

The optical film 10 includes a polarizing plate. As a polarizing plate, the thing by which the suitable transparent protective film was bonded to one side or both sides of a polarizer as needed is generally used. A polarizer is not specifically limited, Various things can be used. As a polarizer, a dichroic substance, such as an iodine or a dichroic dye, is made to adsorb | suck to hydrophilic polymer films, such as a polyvinyl alcohol-type film, a partially formalized polyvinyl alcohol-type film, and an ethylene-vinyl acetate copolymerization partial saponification film, And polyene-based oriented films such as monoaxially stretched, dehydrated polyvinyl alcohol and dehydrochloric acid treated polyvinyl chloride.

In the transparent protective film as a protective film of a polarizer, transparency, mechanical strength, thermal stability, moisture barrier property, and optical properties such as cellulose resin, cyclic polyolefin resin, acrylic resin, phenylmaleimide resin, polycarbonate resin, etc. It is preferably used that is excellent in isotropy. In addition, when the transparent protective film is formed on both surfaces of a polarizer, the protective film containing the same polymer material may be used in the front and back, and the protective film containing a different polymer material etc. may be used. Moreover, optically anisotropic films, such as a retardation plate (stretched film), can also be used as a protective film of a polarizer for the purpose of optical compensation of a liquid crystal cell, expansion of a viewing angle, etc.

The optical film 10 may contain only a polarizing plate, and the other film may be laminated | stacked on one or both surfaces of a polarizing plate through an appropriate adhesive bond layer and an adhesive layer as needed. As such a film, what is used for formation of image display apparatuses, such as a phase difference plate, a viewing angle expansion film, a viewing angle limitation (peep prevention) film, and a brightness enhancement film, is used, The kind in particular is not restrict | limited. For example, in a liquid crystal display device, optical compensation is performed between an image display cell (liquid crystal cell) and a polarizing plate for the purpose of suitably converting the polarization state of the light emitted from the liquid crystal cell to the viewer side and improving the viewing angle characteristic. A film may be used. In the organic EL display device, a quarter wave plate may be disposed between the cell and the polarizing plate in order to suppress external light from being reflected by the metal electrode layer and viewed as a mirror surface. Further, by arranging the quarter wave plate on the viewing side of the polarizing plate and making the emitted light circularly polarized, it is possible to visually recognize the proper image display even for the viewer equipped with polarized sunglasses.

The surface of the optical film 10 may be subjected to a hard coating layer, an antireflection treatment, a sticking prevention, or a treatment for the purpose of diffusion or antiglare. In addition, the surface modification process may be performed on the surface of the optical film 10 for the purpose of adhesive improvement, etc. before laying out the adhesive layers 21 and 22. FIG. Specific treatments include corona treatment, plasma treatment, flame treatment, ozone treatment, primer treatment, glow treatment, saponification treatment, treatment with a coupling agent, and the like. Moreover, you may form an antistatic layer suitably.

<Formation of Optical Film with Adhesive>

The method of forming the laminated pressure sensitive adhesive sheet 20 on the optical film 10 is not particularly limited. The laminated pressure-sensitive adhesive sheet 20 as shown in FIG. 1 may be formed in advance, and the protective sheet 41 on the side of the first pressure-sensitive adhesive layer 21 may be peeled off and bonded onto the optical film 10, or the optical film 10 may be bonded. ), The first pressure sensitive adhesive layer 21 and the second pressure sensitive adhesive layer 22 may be sequentially joined. On the optical film, the composition for forming a first pressure sensitive adhesive layer may be applied to form a first pressure sensitive adhesive layer, and a second pressure sensitive adhesive layer may be formed thereon by coating or transferring. Moreover, a laminated adhesive sheet can be formed on the optical film 10 by coextrusion of the composition for 1st adhesive layer formation and the composition for 2nd adhesive layer formation, and the optical film with an adhesive can also be obtained.

[Optical Film with Double-Sided Adhesive]

The double-sided adhesive as shown in FIG. 3 by forming the laminated pressure-sensitive adhesive sheet 20 of the present invention on one side of the optical film 10 and the other pressure-sensitive adhesive sheet (cell-side adhesive sheet) 26 on the other side. The optical film with which is provided is obtained. In the aspect shown in FIG. 3, the protective sheet 41 is adhere | attached so that peeling is possible on the front side adhesive sheet 20 (lamination adhesive sheet of this invention) of the optical film 55 with a double-sided adhesive, The protective sheet 46 is adhere | attached so that peeling is possible on the cell side adhesive sheet 26. As shown in FIG.

Thus, when using the optical film with a double-sided adhesive in which the adhesive layer was previously attached to both surfaces of the optical film 10, after attaching an optical film to the surface of an image display cell, a separate sheet is laid on an optical film. The process to be made can be omitted, and the manufacturing process of an image display apparatus can be simplified.

<Cell side adhesive sheet>

3 micrometers-30 micrometers are preferable, as for the thickness of the cell side adhesive sheet 26, 5 micrometers-27 micrometers are more preferable, and 10 micrometers-25 micrometers are still more preferable. As the cell side pressure sensitive adhesive sheet, various pressure sensitive adhesives used for bonding an optical film and an image display cell can be used. As an adhesive which comprises a cell side adhesive sheet, an acrylic adhesive is used preferably.

Cell side pressure-sensitive adhesive sheet 26, the storage elastic modulus G _'20 is, more preferably from 1 × 10 ⁴ ㎩ to 1 × 10 ⁷ ㎩ which is preferably, 5 × 10 ⁴ ㎩ to 5 × 10 ⁶ ㎩ at 20 ℃ It is more preferable that it is 1 * 10 <^5> Pa-1 * 10 <^6> Pa. If the cell side of the pressure-sensitive adhesive sheet G _'20 is the above-described range, it is possible to suppress indicated with a suitable adhesive, as of the time of cutting the cut edge, such as adhesive or yichak, such flaring, the defect of the pressure-sensitive adhesive.

[Image display device]

4 is a schematic sectional view illustrating one embodiment of the image display device. The optical film with an adhesive of this invention is equipped with the front transparent member 70, such as a touch panel and a front transparent plate, on one side (viewing side) of the optical film 10 containing a polarizing plate, and the other It is used suitably for formation of the image display apparatus 100 provided with image display cells 61, such as a liquid crystal cell and an organic EL cell, on the surface. The laminated pressure sensitive adhesive sheet 20 of the present invention is used for bonding an optical film 10 including a polarizing plate to a front transparent member 70 such as a touch panel or a front transparent plate.

As the front transparent member 70, a front transparent plate (window layer), a touch panel, etc. are mentioned. As the front transparent plate, a transparent plate having a suitable mechanical strength and thickness is used. As such a transparent plate, transparent resin plates, such as acrylic resin and polycarbonate resin, a glass plate, etc. are used, for example. As a touch panel, the touch panel of arbitrary systems, such as a resistive film system, a capacitive system, an optical system, and an ultrasonic system, is used.

When using the optical film with a double-sided adhesive shown in FIG. 3, the bonding method of the image display cell 61 and the optical film 55 with adhesive was provided, and the front transparent member 70 and adhesive are provided. The bonding method with the attached optical film 55 is not specifically limited, After peeling the protective sheets 41 and 46 adhere | attached on each surface of the front side adhesive sheet 20 and the cell side adhesive sheet 26, It can join by various well-known methods.

The order of bonding is not specifically limited, Bonding of the cell display adhesive sheet 26 of the image display cell 61 and the optical film 55 with an adhesive may be performed first, and the front transparent member 70 and the adhesive may be Bonding with the front side adhesive sheet 20 of the provided optical film 55 may be performed first. In addition, the joining of both can also be performed simultaneously. From the viewpoint of improving the workability of bonding and the axial accuracy of the optical film, the optical film 10 and the image display cell 61 are attached to the adhesive sheet after peeling the protective sheet 46 from the surface of the cell-side adhesive sheet 26. The cell side bonding process bonded together via 26 is performed, and after that, the protective sheet 41 is peeled off from the surface of the front side adhesive sheet 20, and the optical film 10 and the front transparent member 70 are It is preferable that the visual recognition side joining process bonded together through the laminated adhesive sheet 20 is performed.

After the optical film and the front transparent member are bonded together, near the interface between the second pressure sensitive adhesive layer 22 and the front transparent member 70 and non-flat portions such as the printed portion 76 of the front transparent member 70. It is preferable that degassing | defoaming for removing the bubble of is performed. As a defoaming method, the appropriate method, such as heating, pressurization, and pressure reduction, can be employ | adopted. For example, it is preferable that bonding is performed while suppressing mixing of bubbles under reduced pressure and heating, and then pressurization is carried out simultaneously with heating by an autoclave treatment or the like for the purpose of suppressing delay bubbles or the like.

As described above, by using the laminated pressure sensitive adhesive sheet of the present invention and the optical film provided with the pressure sensitive adhesive having the laminated pressure sensitive adhesive sheet, the mixing of bubbles and the occurrence of display irregularities in the vicinity of the printing step of the front transparent member can be suppressed. Can be. In addition, even when outgas from the front transparent member occurs due to use in a high temperature environment, the retention of bubbles on the interface between the front transparent member and the pressure sensitive adhesive sheet is suppressed. Therefore, according to this invention, the image display apparatus excellent in visibility is obtained.

EXAMPLE

Although an Example and a comparative example are given to the following and this invention is demonstrated in detail, this invention is not limited to these Examples.

[Production of adhesive sheet]

<Adhesive sheet A>

(Preparation of Adhesive Composition)

In a reaction vessel including a thermometer, a stirrer, a cooler, and a nitrogen gas introduction tube, 40 parts by weight of 2-ethylhexyl acrylate (2EHA), 40 parts by weight of isostearyl acrylate (ISA) and N-vinylpyrrolidone : 10 parts by weight, 4-hydroxybutyl acrylate: 10 parts by weight, and 1-hydroxy-cyclohexyl-phenyl-ketone (trade name: Irgacure 184, manufactured by BASF Japan): 0.1 part by weight as a photopolymerization initiator Then, ultraviolet rays were irradiated under a nitrogen atmosphere to obtain a prepolymer composition having a polymerization rate of 10%. To this prepolymer, trimethylolpropanetriacrylate (TMPTA): 0.15 parts by weight as a polyfunctional monomer, and 3-glycidoxypropyltrimethoxysilane (trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.): 0.3 as a silane coupling agent. After the weight part was added, these were mixed uniformly and the adhesive composition A was prepared.

(Production of the adhesion sheet)

The adhesive composition A was apply | coated so that one side might be 175 micrometers in thickness, and the coating layer was formed on the peeling process surface of the 75-micrometer-thick polyester film in which peeling process was carried out with silicone, and the thickness which single side | surface single-sided silicon peeling process was carried out on this coating layer. The peeling process surface of the 38 micrometers polyester film was bonded together. Thereafter, from the surface on the polyester film side having a thickness of 38 µm, UV light until the accumulated amount of light reaches 3000 mJ / cm 2 by the black light adjusted to position the irradiation intensity on the irradiation surface under the lamp to be 5 mW / cm 2. It irradiated, superposed | polymerized, and produced the acrylic adhesive sheet A of 175 micrometers in thickness.

<Adhesive sheet B, C, D>

Except having changed the addition monomer composition and the addition amount of a polyfunctional monomer as shown in Table 1, it carried out similarly to the said adhesive composition A, and prepared adhesive compositions B, C, and D. Using this adhesive composition, it carried out similarly to preparation of the said adhesive sheet A, and produced the adhesive sheets B, C, and D with a thickness of 175 micrometers.

<Adhesive sheet E, F>

Except having changed the addition monomer composition and the addition amount of a polyfunctional monomer as shown in Table 1, it carried out similarly to the said adhesive composition A, and prepared adhesive compositions E and F. FIG. Using this pressure-sensitive adhesive composition, pressure-sensitive adhesive sheets E and F were produced in the same manner as in production of pressure-sensitive adhesive sheet A, except that the coating thickness was changed to 25 μm and the accumulated light amount of UV irradiation to 1000 mJ / cm 2.

<Adhesive sheet A1, A2>

Except having changed the application thickness into 200 micrometers and 150 micrometers using the adhesive composition A, it carried out similarly to manufacture of the adhesive sheet A, and produced the adhesive sheets A1 and A2.

<Adhesive sheet B1>

Except having changed the application thickness to 200 micrometers using the adhesive composition B, it carried out similarly to manufacture of the adhesive sheet B, and produced the adhesive sheet B1.

<Adhesive sheet E1>

Except having changed the application thickness to 200 micrometers and the accumulated light quantity of UV irradiation to 3000mJ / cm <2>, using the adhesive composition E, the adhesive sheet E1 was produced like manufacture of the adhesive sheet E.

<Adhesive sheet F1>

The pressure-sensitive adhesive sheet F1 was produced in the same manner as in the production of the pressure-sensitive adhesive sheet F, except that the pressure-sensitive adhesive composition F was used to change the coating thickness to 200 m and the accumulated light amount of UV irradiation to 3000 mJ / cm 2.

<Adhesive sheet F2, F3>

Except having changed the coating thickness into 12 micrometers and 50 micrometers using the adhesive composition F, respectively, it carried out similarly to manufacture of the adhesive sheet F, and produced adhesive sheets F2 and F3.

<Cell side adhesive sheet>

(Preparation of Adhesive Composition)

In a reaction vessel including a thermometer, a stirrer, a cooler, and a nitrogen gas introduction tube, 97 parts by weight of butyl acrylate (BA) and 3 parts by weight of acrylic acid (AA) as a monomer component, and azobisiso as a thermal polymerization initiator. Butyronitrile (AIBN): 0.2 weight part was added with 233 weight part of ethyl acetate, and it stirred for 1 hour in 23 degreeC nitrogen atmosphere, and performed nitrogen substitution. Then, it reacted at 60 degreeC for 5 hours, and obtained the acrylic base polymer whose weight average molecular weight (Mw) is 1.1 million. To this acrylic base polymer solution, trimethylolpropantolylene diisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.): 0.8 parts by weight and a silane coupling agent (trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.): After adding 0.1 weight part, it mixed uniformly and prepared the adhesive composition (solution).

(Production of the adhesion sheet)

The pressure-sensitive adhesive composition was applied on a release treated surface of a polyester film having a thickness of 38 μm and one side was peeled off so that the thickness after drying was 20 μm, dried at 100 ° C. for 3 minutes to remove the solvent, Got. Then, it heated at 50 degreeC for 48 hours, performed crosslinking process, and obtained the cell side adhesive sheet.

[Evaluation Method of Adhesive and PSA Sheet Properties]

<Gel fraction of the adhesive>

The adhesive sheet was cut out to a size of 40 mm x 40 mm, cut into a size of 100 mm x 100 mm, surrounded by a porous polytetrafluoroethylene membrane (NTF-1122, manufactured by Nitto Denko, thickness: 85 µm), and the surrounding inlet was wound ( Thickness 1.5mm x length 100mm). From the weight of this sample, the total weight (A) of the weights of the porous polytetrafluoroethylene membrane and combustion chamber measured beforehand was subtracted, and the weight (B) of the adhesive sample was computed. The pressure-sensitive adhesive sample wrapped in the porous polytetrafluoroethylene membrane was immersed in about 50 mL of ethyl acetate at 23 ° C. for 7 days, and the sol component of the pressure-sensitive adhesive was eluted out of the porous polytetrafluoroethylene membrane. After immersion, the pressure-sensitive adhesive surrounded by the porous polytetrafluoroethylene membrane was taken out, dried at 130 ° C. for 2 hours, allowed to cool for about 20 minutes, and the dry weight (C) was measured. The gel fraction of the adhesive was computed by the following formula.

Gel fraction (%) = 100 × (C-A) / B

<Storage Modulus of Adhesive Sheet>

What laminated | stacked some adhesive sheets and made thickness about 1.5 mm was used as the sample for a measurement. In addition, for the measurement of the storage elastic modulus of a laminated adhesive sheet, what laminated | stacked the 1st adhesive layer and the 2nd adhesive layer alternately, and made it about 1.5 mm in thickness was used as a sample for a measurement. Rheometric Scientific Co., Ltd., "Advanced Rheometric Expansion System (ARES)" by using, according to the following conditions, and subjected to the dynamic viscoelasticity measurement, of the measurement results, 20 ℃, 100 ℃, the storage elastic modulus (G _'20 in 150 ℃, G ' ₁₀₀ , G' ₁₅₀ ) were read.

(Measuring conditions)

Transform Mode: Torsion

Measuring frequency: 1 ㎐

Temperature rise rate: 5 ℃ / min

Measurement temperature: in the range of -50 to 150 ° C

Shape: Parallel Plate 8.0mmφ

<Residual Stress of Adhesive Sheet>

The sheet piece of 40 mm x 40 mm was cut out from the adhesive sheet, it was rolled up in the cylinder shape, and it was set as the measurement sample. The measurement sample was set by adjusting the distance between the chucks in a tensile tester to 20 mm, and tensioned to a strain of 300% (the distance between the chucks is 80 mm) at a tensile rate of 200 mm / min and a measurement temperature of 25 ° C. to fix the chuck position. The stress (tensile stress) after 180 second passed was made into residual stress.

<Weight average molecular weight>

The weight average molecular weight (Mw) of the base polymer was measured by a GPC (Gel Permeation Chromatography) apparatus (product name "HLC-8120GPC" manufactured by Tosoh. The measurement sample was dissolved in tetrahydrofuran to give 0.1 wt% The filtrate filtered using the membrane filter of 0.45 micrometer which used as the solution was used.

(Measuring conditions)

Column: Tosoh Corporation, G7000HXL + GMHXL + GMHXL

Column size: Each 7.8 mm φ x 30 cm (total column length: 90 cm)

Column temperature: 40 ° C, flow rate: 0.8 mL / min

Injection volume: 100 μL

Eluent: tetrahydrofuran

Detector: Differential Refractometer (RI)

Standard sample: polystyrene

[Evaluation Results of Adhesive Sheet (Single Layer)]

Table 1 shows the composition of the pressure-sensitive adhesive of the pressure-sensitive adhesive sheets A to F and the physical properties of the pressure-sensitive adhesive sheet (single layer). In addition, in Table 1, each component is described by the following abbreviations.

2EHA: 2-ethylhexyl acrylate

ISA: isostearyl acrylate

MMA: Methyl methacrylate

AA: acrylic acid

NVP: N-vinylpyrrolidone

VA: Vinyl Acetate

4HBA: 4-hydroxybutyl acrylate

2HEA: 2-hydroxyethyl acrylate

TMPTA: trimethylolpropane triacrylate

Example 1

As an optical film, the polarizing plate provided with the transparent protective film on both surfaces of the polarizer containing the stretched polyvinyl alcohol film of thickness 25micrometer in which iodine was impregnated was used. The said cell side adhesive sheet was bonded to one surface (surface of a cell side) of a polarizing plate using a roll laminator. Then, the said adhesive sheet A was bonded to the other surface (surface of the visual recognition side) of a polarizing plate using a roll laminator. Moreover, the said adhesive sheet E was bonded on the adhesive sheet A using the roll laminator. Thus, one side of a polarizing plate was provided with the cell side adhesive sheet, and the other side of the polarizing plate was provided with the laminated adhesive sheet of the adhesive sheet A and the adhesive sheet E, and the surface of the cell side adhesive sheet and the laminated adhesive sheet of the visual recognition side of the The polarizing plate with a double-sided adhesive with which the protective film was temporarily mounted on each surface was obtained.

[Examples 2 to 7, Comparative Example 1]

Except having changed the structure of the adhesive sheet bonding to the visual side of a polarizing plate as shown in Table 2, it carried out similarly to the said Example 1, and obtained the polarizing plate with a double-sided adhesive.

[Comparative Examples 2 to 5]

A double-sided adhesive was provided in the same manner as in Example 1 except that the pressure-sensitive adhesive sheet bonded to the visual side of the polarizing plate was changed to a 200-micrometer-thick pressure-sensitive adhesive sheet containing single layers of pressure-sensitive adhesive sheets A1, B1, C1, and D1. A polarizing plate was obtained.

[evaluation]

<Plastic bubble reliability>

After cutting the polarizing plate with a double-sided adhesive into the size of 45 mm x 80 mm, the protective film of the visual side was peeled off, and it was a hand roller on the surface hardening acrylic board (Mitsubishi Rayon-made acrylic light MR-200) of thickness 1mm. It bonded together using the autoclave process (50 degreeC, 0.5 Mpa, 15 minutes). After heating this sample for 24 hours in the 85 degreeC drying oven, it took out from the oven, visually confirmed the external appearance, and it confirmed that the bubble was not seen, and that the bubble which did not make a foreign material a nucleus was confirmed as x. .

<Display unevenness>

(Production of image display apparatus for evaluation)

The backlight portion was removed from the upper liquid crystal panel for replacing the Nintendo 3DS, the polarizing plate opposite to the backlight of the liquid crystal panel was removed, and then the adhesive on the surface of the liquid crystal cell was removed using a clean cloth in which ethanol was soaked. After cutting the polarizing plate with double-sided adhesive into the size of 50 mm x 80 mm, the protective film of the cell side surface was peeled off, the cell side adhesive sheet surface was superimposed on the center part of the liquid crystal cell surface, and it bonded using the hand roller.

Thereafter, the protective film on the viewing side of the polarizing plate with double-sided adhesive was peeled off, and the glass plate (0.7 mm x 50 mm x 100 mm, ink print thickness = 15 µm, both sides printed with black ink in a frame shape on the periphery) Ink printing width of each side (long side direction): 15 mm each, ink printing width of both long sides (short side direction): 5 mm) The printing surface of each side is mounted on the exposed surface of an adhesive, and a vacuum thermocompression bonding apparatus is carried out. Bonding was carried out (temperature 25 ° C., pressure 50 kPa in the apparatus, pressure 0.3 MPa, pressure holding time 10 seconds). Then, autoclave process (50 degreeC, 0.5 Mpa, 15 minutes) was performed. Thus, the evaluation panel obtained was exchanged with the image display panel of the Nintendo 3DS main body, and was electrically connected, and the image display apparatus for evaluation was obtained. The presence or absence of display nonuniformity in the vicinity of a printing frame when the panel was made white display was visually confirmed. (Circle) that the display nonuniformity was not recognized and (triangle | delta) and the thing which confirmed the display nonuniformity easily were shown by (circle) that the display nonuniformity was seen a little.

<Clouding of the adhesive sheet in a high humidity environment>

The said image display apparatus for evaluation was thrown in for 60 hours in 60 degreeC 95% RH constant temperature and humidity tank. Then, the sample was taken out and it checked visually the presence or absence of the turbidity of an adhesive layer after storing for 24 hours in 25 degreeC 50% environment. In Examples 1 to 6, the cloudiness of the pressure-sensitive adhesive layer was not seen, but in Example 7 in which both the first pressure sensitive adhesive layer and the second pressure sensitive adhesive layer did not contain a hydroxyl group-containing monomer in the base polymer, cloudiness was confirmed. From this result, it turned out that cloudiness at the time of exposing an adhesive sheet to a high humidity environment can be suppressed by using a hydroxyl group containing monomer for a base polymer.

<Interlayer Peel Test of Laminated Adhesive Sheet>

The 1st adhesive layer and the 2nd adhesive layer were bonded together using the hand roll, and the laminated adhesive sheet was produced. This laminated adhesive sheet is cut out to width 25mm x length 100mm, the polyester film of width 25mm x length 250mm x thickness 25micrometer is bonded to the surface of the 1st adhesive layer side, and the surface of the 2nd adhesive layer side, What was bonded to the glass plate using the hand roller was used as the test piece. Using the tensile tester, the edge part of the glass plate and the edge part of a polyester film were hold | maintained by the chuck, 180 degree peeling of the polyester film was performed at the tensile speed of 1000 mm / min, and it confirmed that at which interface peeling occurred. . The thing with which peeling generate | occur | produced in the interface of a 1st adhesive layer and a 2nd adhesive layer was "no interlayer peeling", and the thing which peeled at the interface of glass and a 2nd adhesive layer was "no interlayer peeling".

In Example 1-7 and the comparative example 1, the interlayer peeling between adhesive layers was not seen. On the other hand, in Example 1, 2, instead of adhesive A, similar evaluation was performed using adhesive A 'which does not contain a silane coupling agent, and the interlayer peeling was seen. In addition, in Example 3, 4, even when adhesive B 'which does not contain a silane coupling agent was used instead of adhesive B, the interlayer peeling was seen. When adhesive E 'which does not contain a silane coupling agent is used instead of adhesive E in Examples 1 and 3, and adhesive F' which does not contain a silane coupling agent instead of adhesive F in Examples 2 and 4, Even when used, interlayer peeling was observed. From these results, in order to suppress the interlayer peeling of an adhesive, it turns out that it is effective to contain a silane coupling agent in both of the 1st adhesive layer and the 2nd adhesive layer which comprise a laminated adhesive sheet.

[Evaluation results]

Laminated structure of the visual-side adhesive layer in the polarizing plate with double-sided pressure-sensitive adhesive of each of the above Examples and Comparative Examples, physical properties of the laminated pressure-sensitive adhesive sheet (However, Comparative Examples 2 to 5 are the characteristics of the pressure-sensitive adhesive sheet of the single layer), and bubble reliability and Table 2 shows the evaluation results of the display nonuniformity.

In Comparative Examples 2 to 5 in which a single pressure-sensitive adhesive sheet was used as the visual-side pressure-sensitive adhesive layer, it can be seen that the evaluation results of any one of bubble reliability and display unevenness were ×, and these were not compatible. Moreover, in the comparative example 1, since the storage elastic modulus at the high temperature of the 1st adhesive layer arrange | positioned at the polarizing plate side of a laminated adhesive sheet was high, and the storage elastic modulus at the high temperature as the whole laminated adhesive sheet was also high, display unevenness was seen.

On the other hand, in Examples 1-7, all the evaluation results of bubble reliability and display nonuniformity were (circle). Storage at 150 ℃ of the laminated adhesive sheet elastic modulus of 1 × 10 ⁴ Pa is less than Examples 1 to 3 and Example 5, Example 4,6 The storage elastic modulus at 150 ℃ of the multilayer pressure-sensitive adhesive sheet not less than 1 × 10 ⁴ Pa In comparison with, 7, display unevenness is more difficult to visually recognize.

As for Example 3 and Example 4, although the adhesive sheet B was used as a 1st adhesive layer formed in the polarizing plate side, the adhesive sheet E used as a 2nd adhesive layer in Example 3 was used in Example 4, Compared with the adhesive sheet F, the storage elastic modulus at high temperature is low. Therefore, in Example 3, since the storage elastic modulus at the high temperature of the whole laminated adhesive sheet is low compared with Example 4, it is thought that display unevenness was further suppressed.

In Example 2 and Example 6, although the composition of both a 1st adhesive layer and a 2nd adhesive layer is the same, since the thickness ratio of both differs, Example 2 has a low storage elastic modulus at the high temperature of a laminated adhesive sheet whole, It is thought that display unevenness was further suppressed.

From the above results, in addition to using a low storage elastic modulus at a high temperature as the first pressure sensitive adhesive layer formed on the polarizing plate side, the occurrence of display irregularities can be further suppressed by lowering the storage elastic modulus at a high temperature of the entire adhesive sheet. It can be seen.

10: optical film
20: Front side adhesive sheet (laminated adhesive sheet)
21, 22: adhesive layer
26: cell side adhesive sheet
41, 42, 46: protective sheet
53, 55: optical film with pressure-sensitive adhesive
61: image display cell
70: front transparent member
71: plate-shaped transparent member
76: printing
100: image display device

Claims (14)

It is an optical film with an adhesive used for arrange | positioning between a front transparent plate or a touch panel, and an image display cell,
An optical film including a polarizing plate, and a front side adhesive sheet formed on one surface of the optical film,
The said front side adhesive sheet is a laminated adhesive sheet in which at least two adhesive layers were laminated | stacked, and is provided with the 1st adhesive layer arrange | positioned in contact with the said optical film, and the 2nd adhesive layer arrange | positioned most apart from the said optical film. and,
The first pressure-sensitive adhesive layer has a storage elastic modulus at 150 ℃ 9 × 10 ³ and ㎩ or less, a storage elastic modulus G _'20 to the storage elastic modulus G of from ₁₅₀ ℃' 150 ratio G _'20 / G' of from 20 ℃ ₁₅₀ Is over 20,
The said 2nd adhesive layer is an optical film with an adhesive whose storage elastic modulus in 20 degreeC is 4 * 10 <^5> Pa or less, and whose storage elastic modulus in 150 degreeC is 1 * 10 <^4> Pa or more. The method of claim 1,
The optical film with an adhesive whose storage elastic modulus at 150 degrees C of the said front side adhesive sheet is 1 * 10 <^4> Pa or less. The method of claim 1,
The optical film with an adhesive with which the gel fraction of the said 2nd adhesive layer is larger than the gel fraction of the said 1st adhesive layer. The method of claim 3,
The optical film with an adhesive whose difference between the gel fraction of the adhesive of the said 1st adhesive layer and the gel fraction of the adhesive of the said 2nd adhesive layer is 15 weight% or more. The method according to any one of claims 1 to 4,
The optical film with an adhesive of the said 1st adhesive layer whose gel fraction of an adhesive is 55 weight% or less. The method according to any one of claims 1 to 4,
The said 2nd adhesive layer is an optical film with an adhesive whose gel fraction of an adhesive is 75 weight% or more. The method according to any one of claims 1 to 4,
The pressure-sensitive adhesive of the first pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing an acrylic base polymer,
The optical film with adhesive which the said acrylic base polymer of the said 1st adhesive layer contains 1 or more types chosen from the group which consists of a hydroxyl group containing monomer and a nitrogen containing monomer as a monomer unit. The method according to any one of claims 1 to 4,
The pressure-sensitive adhesive of the second pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing an acrylic base polymer,
The optical film with adhesive which the said acrylic base polymer of a said 2nd adhesive layer contains 1 or more types chosen from the group which consists of a nitrogen containing monomer and a carboxyl group containing monomer as a monomer unit. The method according to any one of claims 1 to 4,
The said 1st adhesive layer and the said 2nd adhesive layer are both optical films with an adhesive with a silane coupling agent. The method according to any one of claims 1 to 4,
The optical film with an adhesive whose thickness of a said 1st adhesive layer is 40 micrometers or more. The method according to any one of claims 1 to 4,
The optical film with an adhesive whose thickness of the said 2nd adhesive layer is 5 micrometers-70 micrometers. The method according to any one of claims 1 to 4,
The first pressure-sensitive adhesive layer thickness d ₁ and a second thickness of the pressure-sensitive adhesive layer d ₂ ratio d ₁ / d ₂ of 2 to 40 is, the optical film comprising the pressure-sensitive adhesive. The optical film with an adhesive as described in any one of Claims 1-4 WHEREIN: The optical film with a double-sided adhesive which further comprises a cell side adhesive sheet in the other surface of the said optical film. On the surface of an image display cell, the optical film with an adhesive as described in any one of Claims 1-4, and a front transparent plate or a touch panel are provided,
An image display device, wherein the optical film and the front transparent plate or touch panel are bonded to each other by the front side adhesive sheet.

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